The present invention relates to an air scrubbing device for contamination removal and its uses thereof. More specifically, the present invention relates to device installed in a central air conditioning system, used as a floor or wall mountable device, or a device attached to respirators that employs an alkali solution to remove airborne contaminants (e.g., microorganisms, viruses, allergens, toxins, warfare chemicals and biological agents) from air entering the device and thus decontaminating the environment in which the device is positioned or supplying air to. Contaminants hazardous to health and interfering in a variety of manufacturing operations include:                1. Environmental Chemicals: Air contamination, particularly indoor air contamination, contributes to human health complications. Specifically, airborne chemical contaminants, particularly when present in poorly ventilated areas, cause a wide variety of human illnesses.                    a. Example chemical contaminants include, byway of non-limiting example, formaldehyde, aerosols, toluene, hydrocarbons, carbon monoxide, and the like, and are known to cause such health complications as eye irritation, headaches, nose and/or mucosal irritation, fatigue and the like.            b. Example Biological Agents: Air contamination, particularly indoor air contamination, contributes to human health complications. Specifically, airborne biological contaminants, particularly when present in poorly ventilated areas, cause a wide variety of human illnesses. Example biological contaminants include, by way of non-limiting example, bacteria, fungi, yeast, prions, fungi spores, protozoa, viruses, algae, pollen, various antigenic agents, and the like, and are known to cause such health complications as pneumonia, fever, mycotoxicosis, various infections, asthma and the like. One of the most perplexing health problems arises from nosocomial or hospital-acquired infections from sick patients adding substantially to the cost of healthcare. Whereas general hospital working practices are aimed at reducing these infections and whereas hospitals practice isolation of dangerously infections patients, these efforts have generally been ineffective; one of the most widely known diseases resulting from nosocomial spread of infection was Legionnaires disease. The annual cost of treatment resulting from nosocomial infection in the US is between $4 Billion to $11 Billion; this cost can be substantially reduced by practicing the present invention through which the air around contaminating patients can be kept sterilized and thus preventing the spread rather than attempting to control it once it spreads through the air conditioning systems of the hospitals.                        2. Environmental allergens: An important area of concern is the management of a large number of respiratory disorders emanating from allergens in the air. The pollen season wrecks havoc on the health of billions of people, adding over a $100 Billion to health care cost per year and inflicting misery to a large percentage of the world population. An allergen is typically a protein associated with a carbohydrate chain and is carried out in the air by floating particles or as pollens. While the outdoor exposure to these allergens is not preventable, the indoor environments can be made almost allergen free and to do this several devices have been suggested, mostly comprising of filtering the air either by physical filters (which remain ineffective) or by electronic precipitation, which remains extremely expensive if adequately installed.                    a. Outdoor allergens: Pollens and mold spores are outdoor allergens that float in the air and commonly trigger nasal allergy symptoms. Pollen is a microscopic, powdery substance used by plants for fertilization and reproduction. Pollens are carried between plants by wind, water, animals, bees and other insects. Nasal allergy symptoms are more often triggered by plants with small pollens that are spread by wind currents such as trees, grasses, and weeds. Generally, the pollens from brightly flowered plants with larger pollen grains don't trigger nasal allergies. Molds are microscopic members of the fungus family, which also includes mushrooms. Mold spores travel through the air like pollen. However, unlike pollen, they do not have a specific season but tend to thrive in moist situations and are affected by wind or rain. Outdoor mold spores begin to appear after a spring thaw and typically peak between July and October. In regions with mild winters, outdoor molds can be found all year long.            b. Indoor Allergens: Indoor, or perennial, nasal allergies are triggered by another group of allergens, including dust mites, animal dander and urine, cockroach droppings, and indoor molds. Animals with fur or feathers can cause nasal allergy symptoms trigerred by saliva, proteins in animals' dander (dead skin), and urine that cause nasal allergy problems. Dust mites are microscopic creatures that live in dust and consume discarded flakes of human skin. Dust mite droppings are a common trigger of nasal allergy symptoms, and are found throughout homes, especially in parts of the home with high humidity or a concentration of human skin flakes, such as mattresses or pillows. Indoor molds thrive in dark, damp places such as basements and bathrooms. When these molds release airborne spores, they can trigger nasal allergy symptoms. Several species of cockroaches live in homes and other buildings, especially in urban areas, and especially where food and water can be found readily. Experts believe that cockroaches' bodies, as well as their feces and saliva, can trigger nasal allergies.                        3. Biological Warfare Agents: Biological warfare is the deliberate use of disease and natural poisons to incapacitate humans. It employs pathogens as weapons. Pathogens are the microorganism, whether bacterial, viral or protozoic, those cause disease. There are four kinds of biological warfare agents: bacteria, viruses, rickettsiae and fungi. Biological weapons are distinguished by being living organisms, that reproduce within their host victims, who then become contagious with a deadly, if weakening, multiplier effect. Toxins in contrast do not reproduce in the victim and need only the briefest of incubation periods; they kill within a few hours. Diseases considered for weaponization, or known to be weaponized include anthrax, ebola, Marburg virus, plague, cholera, tularemia, brucellosis, Q fever, machupo, Coccidioides mycosis, Glanders, Melioidosis, Shigella, Rocky Mountain spotted fever, typhus, Psittacosis, yellow fever, Japanese B encephalitis, Rift Valley fever, and smallpox. Naturally occurring toxins that can be used as weapons include ricin, SEB, botulism toxin, saxitoxin, and many mycotoxins. Include inhaled        4. Chemical Warfare Agents: Chemical warfare is different from the use of conventional weapons or nuclear weapons because the destructive effects of chemical weapons are not primarily due to any explosive force. The offensive use of living organisms (such as anthrax) is considered biological warfare rather than chemical warfare; however, the use of nonliving toxic products produced by living organisms (e.g. toxins such as botulinum toxin, ricin, and saxitoxin) is considered chemical warfare under the provisions of the Chemical Weapons Convention. Under this Convention, any toxic chemical, regardless of its origin, is considered a chemical weapon unless it is used for purposes that are not prohibited (an important legal definition known as the General Purpose Criterion).                    a. Nerve Agents: Highly poisonous chemicals that work by preventing the nervous system from working properly: G agents (Sarin (GB), Soman (CD), Tabun (GA)), V agents, (VX)            b. Pulmonary agents (Mustards: Distilled mustard (HD), Mustard gas (H) (sulfur mustard), Mustard/lewisite (HL), Mustard/T, Nitrogen mustard (HN-1, HN-2, HN-3), Sesqui mustard, Sulfur mustard (H) (mustard gas); Lewisites/chloroarsine agents: Lewisite (L, L-1, L-2, L-3), Mustard/lewisite (HL); Phosgene oxime (CX)            c. Poisons that come from plants: (Abrin, Brevetoxin, Colchicine, Digitalis, Nicotine, Ricin, Saxitoxin, Strychnine, Tetrodotoxin, Trichothecene            d. Blood Agents: Arsine (SA), Carbon Monoxide, Cyanide (Cyanogen chloride (CK), Hydrogen cyanide (AC), Potassium cyanide (KCN), Sodium cyanide (NaCN), Sodium monofluoroacetate (compound 1080)            e. Caustics (Acids): Chemicals that burn or corrode people's skin, eyes, and mucus membranes (lining of the nose, mouth, throat, and lungs) on contact such as Hydrofluoric acid (hydrogen fluoride)            f. Choking/Lung/Pulmonary Agents: Chemicals that cause severe irritation or swelling of the respiratory tract (lining of the nose, throat, and lungs): Ammonia, Bromine (CA), Chlorine (CL), Hydrogen chloride, Methyl bromide, Methyl isocyanate, Osmium tetroxide, Phosgene (Diphosgene (DP), Phosgene (CG)), Phosphine, Phosphorus, elemental, white or yellow, Sulfuryl fluoride.                        5. Riot Control Agents/Tear Gas: Highly irritating agents normally used by law enforcement for crowd control or by individuals for protection (for example, mace): Bromobenzylcyanide (CA), Chloroacetophenone (CN), Chlorobenzylidenemalononitrile (CS), Chloropicrin (PS), Dibenzoxazepine (CR). Effective protective gear to protect against these agents while using them is required.        Specialized protections arise when exposed to above and all other agents:                    a. A variety of scientific and medical procedures result in biological contaminants that must be contained. Safety of personnel working in laboratories handling dangerous organisms is of great concern and while specific recommendations on the design of various BSL level laboratories are strictly followed, the most effective means of preventing spread of contamination is to remove it from entering any air distribution system.            b. Clean room environment for manufacturing drugs and other products is achieved by reducing the number of particles that can carry these agents. This is an expensive and often difficult to maintain protocol. In general, biological contamination renders the air in clean rooms inappropriate for manufacturing certain drugs and dosage forms, more particularly biological drugs where removal of viruses and prions is of very high priority and is generally achieved through control of air quality comprising of HEPA filter systems that are difficult and expensive to maintain. In some instances where viral clearance is of great importance, providing sterilized air, free from viruses and prions can prove very useful and cost-effective means of increasing the safety of the products manufactured.            c. Clean environment is also needed for surgery rooms. More particularly, the clean room environment can be created in the field or in those situations where elaborate electrical devices are impossible to install; for example, in the surgery rooms at the battle front, in parts of the world where means of providing hygienic environment are not present and in general, any operation that benefits from clean air is difficult to provide.                        
Prevention of exposure to above chemical and biological agents is of prime importance and a variety of measures are currently available that either selectively or generally reduces exposure or entry into body of these agents.
There is therefore an unmet need to invent a method of scrubbing air fed into air conditioning systems, in confined spaces where contaminants are present, as a first line of defense in chemical and biological weapons use and in a particularly the space where a sensitive product is manufactured and where patients need to be isolated in the event of epidemics. An invention that would resolve the unmet need would be useful in a fixed configuration as well as in a mobile situation for use in the field, examples of which include:                1. Hospital acquired infections. Fixed use in a healthcare facility to prevent cross contamination from one patient to another.        2. Allergan removal. Fixed use in a home to prevent reaction to allergens.        3. Patient Isolation. An area of medical importance is the requirement of sterile, allergan-free air for patients whose immunity has been seriously compromised and they must therefore be restricted to spaces that receive filtered air; the cost of such filtration is very high in the initial capital cost as well as the maintenance; there is thus a need to develop a highly effective, extremely low-cost device to provide this protection to patients.        4. Clean air supply in surgical theaters, manufacturing operations, etc.        5. Field use in the event of biological warfare and bioterrorism attacks. Biological warfare and bioterrorism is of major concern to many sovereign nations and billions of dollars are spent on preventing and confronting combat situations involving biological organisms. The most commonly used approach is to use specialized inhalation equipment that is often cumbersome to use, expensive to acquire and distribute and when used improperly, ineffective. The new invention should substantially reduce the cost of these preventive systems and provide a greater utility such as in the bunkers created to house personnel during an attack where the air supply can be continuously decontaminated of all types of biological agents at a very low cost.        6. Field use in the event of chemical warfare and terrorism attacks. An area of significant concerned is the protection of personnel in the event of chemical warfare attack or in the event of terrorist attacks; whereas suitable respiratory apparatus is available to protect the emergency response teams, the uncertainty in predicting the nature of biological and chemical weapons and the risk of a respirator apparatus failing can be catastrophic.        
Prior art air scrubbing devices suffer from a number of problems. First, the devices are large and consume significant amounts of space and energy to be effective, the extent of which is rarely as complete as required in various sensitive areas of climate control.
The air scrubbing device of the present invention is particularly configured to overcome one or more of the aforementioned problems in removing and/or generally reducing the presence of air borne contaminants to thereby provide a safer, healthier and less infection-prone environment. The present invention also offers an extremely cost-effective approach, whose effectiveness can be further improved by combining with existing systems of HEPA filters and other control systems in practice today.
The instant invention provides a surprisingly broad range of exposure prevention that includes following features, heretofore not available in any single device:                1. Disintegration of biological organisms, spores, allergens and other resilient forms as the high pH dissolves the cell wall and otherwise disintegrates any proteins and other structures.        2. Hydrolysis of most potent organic chemicals because of the high pH effect, regardless of the solubility of compounds.        3. Neutralization of acidic components such as sulfur dioxide in the air.        4. Dissolution of water-soluble agents including gases and retention into liquid phase.        
The functionality aspect of the instant invention include:                1. Fine dispersion of air into sodium hydroxide solution for maximum exposure and scrubbing action.        2. No large bubbles those are more likely to carry air droplets containing sodium hydroxide. The ceramic sparger in the device provides a critical function of dispersing air as fine bubbles in the range of 120-500 microns and thus increasing the contact of air to the surrounding sterilizing liquid;        
the fine air bubbles also take longer time to rise to the surface and thus the total contact time is also increased.                3. A system of removing all airborne alkali solution droplets to reduce risk of exposure to the alkali used.        4. A means of replacing the evaporated water from the solution continuously. At 25 C vapor pressure of 10% sodium hydroxide solution is about 22 mm mercury compared to about 25 mm for water.        5. A means of draining the liquid in the container.        
Chemicals have long been used in sterilization practices where heat will damage heat-sensitive materials such as biological materials, fiber optics, electronics, and many plastics. Low temperature gas sterilizers function by exposing the articles to be sterilized to high concentrations (typically 5-10% v/v) of very reactive gases (alkylating agents such as ethylene oxide, and oxidizing agents such as hydrogen peroxide and ozone). Liquid sterilants and high disinfectants typically include oxidizing agents such as hydrogen peroxide and peracetic acid and aldehydes such as glutaraldehyde and more recently o-phthalaldehyde. While the use of gas and liquid chemical sterilants/high level disinfectants avoids the problem of heat damage, users must ensure that article to be sterilized is chemically compatible with the sterilant being used. The chemicals used as sterilants are designed to destroy a wide range of pathogens and typically the same properties that make them good sterilants makes them harmful to humans. Employers have a duty to ensure a safe work environment (Occupational Safety and Health Act of 1970, section 5 for United States) and work practices, engineering controls and monitoring should be employed appropriately.
Ethylene oxide (EO or EtO) gas is commonly used to sterilize objects sensitive to temperatures greater than 60° C. such as plastics, optics and electrics. Ethylene oxide treatment is generally carried out between 30° C. and 60° C. with relative humidity above 30% and a gas concentration between 200 and 800 mg/L for at least three hours. Ethylene oxide penetrates well, moving through paper, cloth, and some plastic films and is highly effective. Ethylene oxide sterilizers are used to process sensitive instruments, which cannot be adequately sterilized by other methods. Ethylene oxide can kill all known viruses, bacteria and fungi, including bacterial spores and is satisfactory for most medical materials, even with repeated use. However it is highly flammable, and requires a longer time to sterilize than any heat treatment. The process also requires a period of post-sterilization aeration to remove toxic residues. Ethylene oxide is the most common sterilization method, used for over 70% of total sterilizations, and for 50% of all disposable medical devices.
The two most important ethylene oxide sterilization methods are: (1) the gas chamber method and (2) the micro-dose method. To benefit from economies of scale, Ethylene oxide has traditionally been delivered by flooding a large chamber with a combination of Ethylene oxide and other gases used as diluents (usually CFCs or carbon dioxide). This method has drawbacks inherent to the use of large amounts of sterilant being released into a large space, including air contamination produced by CFCs and/or large amounts of ethylene oxide residuals, flammability and storage issues calling for special handling and storage, operator exposure risk and training costs
Because of these problems a micro-dose sterilization method was developed in the late 1950s, using a specially designed bag to eliminate the need to flood a larger chamber with Ethylene oxide. This method is also known as gas diffusion sterilization, or bag sterilization. This method minimizes the use of gas. Ozone is used in industrial settings to sterilize water and air, as well as a disinfectant for surfaces. It has the benefit of being able to oxidize most organic matter. On the other hand, it is a toxic and unstable gas that must be produced on-site, so it is not practical to use in many settings. Ozone offers many advantages as a sterilant gas; ozone is a very efficient sterilant because of its strong oxidizing properties (E=2.076 vs. SHE, CRC Handbook of Chemistry and Physics, 76th Ed, 1995-1996) capable of destroying a wide range of pathogens, including prions without the need for handling hazardous chemicals since the ozone is generated within the sterilizer from medical grade oxygen. The downside of using ozone is that the gas is very reactive and very hazardous. The NIOSH immediately dangerous to life and health limit for ozone is 5 ppm, much 160 times smaller than the 800 ppm IDLH for ethylene oxide. Documentation for Immediately Dangerous to Life or Health Concentrations (IDLH): NIOSH Chemical Listing and Documentation of Revised IDLH Values (as of Mar. 1, 95) and OSHA has set the PEL for ozone at 0.1 ppm calculated as an eight hour time weighted average (29 CFR 1910.1000, Table Z-1).
Chlorine bleach is another accepted liquid sterilizing agent. Household bleach consists of 5.25% sodium hypochlorite. It is usually diluted to 1/10 immediately before use; however to kill Mycobacterium tuberculosis it should be diluted only 1/5, and 1/2.5 (1 part bleach and 1.5 parts water) to inactivate prions. The dilution factor must take into account the volume of any liquid waste that it is being used to sterilize. Bleach will kill many organisms immediately, but for full sterilization it should be allowed to react for 20 minutes. Bleach will kill many, but not all spores. It is highly corrosive and may corrode even stainless steel surgical instruments. Bleach decomposes over time when exposed to air, so fresh solutions should be made daily.
Glutaraldehyde and formaldehyde solutions (also used as fixatives) are accepted liquid sterilizing agents, provided that the immersion time is sufficiently long. To kill all spores in a clear liquid can take up to 12 hours with glutaraldehyde and even longer with formaldehyde. The presence of solid particles may lengthen the required period or render the treatment ineffective. Sterilization of blocks of tissue can take much longer, due to the time required for the fixative to penetrate.
Glutaraldehyde and formaldehyde are volatile, and toxic by both skin contact and inhalation. Glutaraldehyde has a short shelf life (<2 weeks), and is expensive. Formaldehyde is less expensive and has a much longer shelf life if some methanol is added to inhibit polymerization to paraformaldehyde, but is much more volatile. Formaldehyde is also used as a gaseous sterilizing agent; in this case, it is prepared on-site by depolymerization of solid paraformaldehyde. Many vaccines, such as the original Salk polio vaccine, are sterilized with formaldehyde.
Ortho-phthalaldehyde (OPA) is a chemical sterilizing agent that received Food and Drug Administration (FDA) clearance in late 1999. Typically used in a 0.55% solution, OPA shows better myco-bactericidal activity than glutaraldehyde. It also is effective against glutaraldehyde-resistant spores. OPA has superior stability, is less volatile, and does not irritate skin or eyes, and it acts more quickly than glutaraldehyde. On the other hand, it is more expensive, and will stain proteins (including skin) gray in color.
Hydrogen peroxide is another chemical sterilizing agent. It is relatively non-toxic when diluted to low concentrations, such as the familiar 3% retail solutions although hydrogen peroxide is a dangerous oxidizer at high concentrations (>10% w/w). Hydrogen peroxide is strong oxidant and these oxidizing properties allow it to destroy a wide range of pathogens and it is used to sterilize heat or temperature sensitive articles such as rigid endoscopes. In medical sterilization hydrogen peroxide is used at higher concentrations, ranging from around 35% up to 90%.
The best advantage of hydrogen peroxide as a sterilant is the short cycle time. Whereas the cycle time for ethylene oxide (discussed above) may be 10 to 15 hours, the use of very high concentrations of hydrogen peroxide allows much shorter cycle times. Since hydrogen peroxide is a strong oxidant, there are material compatibility issues and users should consult the manufacturer of the article to be sterilized to ensure that it is compatible with this method of sterilization. Paper products cannot be sterilized in the Sterrad system because of a process called cellulostics, in which the hydrogen peroxide would be completely absorbed by the paper product. The penetrating ability of hydrogen peroxide to not as good as ethylene oxide and so there are limitations on the length and diameter of lumens that can be effectively sterilized and guidance is available from the sterilizer manufacturers.
While hydrogen peroxide offers significant advantages in terms of throughput, as with all sterilant gases, sterility is achieved through the use of high concentrations of reactive gases. Hydrogen peroxide is primary irritant and the contact of the liquid solution with skin will cause bleaching or ulceration depending on the concentration and contact time. The vapor is also hazardous with the target organs being the eyes and respiratory system. Even short term exposures can be hazardous and NIOSH has set the Immediately Dangerous to Life and Health Level (IDLH) at 75 ppm, less than one tenth the IDLH for ethylene oxide (800 ppm). Prolonged exposure to even low ppm concentrations can cause permanent lung damage and consequently OSHA has set the permissible exposure limit to 1.0 ppm, calculated as an 8 hour time weighted average (29 CFR 1910.1000 Table Z-1). Employers thus have a legal duty to ensure that their personnel are not exposed to concentrations exceeding this PEL. Even though the sterilizer manufacturers go to great lengths to make their products safe through careful design and incorporation of many safety features, workplace exposures of hydrogen peroxide from gas sterilizers are documented in the FDA MAUDE database. When using any type of gas sterilizer, prudent work practices will include good ventilation (10 air exchanges per hour), a continuous gas monitor for hydrogen peroxide as well as good work practices and training. Further information about the health effects of hydrogen peroxide and good work practices is available from OSHA and the ATSDR.
Dry sterilization process (DSP) uses hydrogen peroxide at a concentration of 30-35% under low-pressure conditions. This process achieves bacterial reduction of 10-6 . . . 10-8. The complete process cycle time is just 6 seconds, and the surface temperature is increased only 10-15° C. (18 to 27° F.). Originally designed for the sterilization of plastic bottles in the beverage industry, because of the high germ reduction and the slight temperature increase the dry sterilization process is also useful for medical and pharmaceutical applications.
Peracetic acid (0.2%) is used to sterilize instruments.
Prions are highly resistant to chemical sterilization. Treatment with aldehydes (e.g., formaldehyde) has even shown to increase prion resistance. Hydrogen peroxide (3%) for one hour was shown to be ineffective, providing less than 3 logs reduction in contamination. Iodine, formaldehyde, glutaraldehyde and peracetic acid also fail this test (one hour treatment). Only chlorine, a phenolic compound, guanidinium thiocyanate, and sodium hydroxide reduce prion levels by more than 4 logs.
Chlorine and sodium hydroxide are the most consistent agents for prions. Chlorine is too corrosive to use on certain objects.
Silver ions and silver compounds show a toxic effect on some bacteria, viruses, algae and fungi, typical for heavy metals like lead or mercury, but without the high toxicity to humans that is normally associated with these other metals. Its germicidal effects kill many microbial organisms in vitro, but testing and standardization of silver products is yet difficult.
Alkalis (bases) like sodium hydroxide, potassium hydroxide, sodium metabisilicate and sodium bicarbonate are defined as alkalis or bases capable of forming hydroxide ions when dissolved in water giving a pH of greater than 7. Alkaline conditions inhibit the growth of microorganisms by restricting various metabolic processes; the structure and function of some macromolecules including enzymes, are particularly affected. At high concentration, alkalis cause the solubilization of bacterial cell walls and membranes and viral envelopes between pH 9 to 11. The reactions of alkalis with various types of lipoids (including phospholipids) in these membranes can be compared to their reaction with fatty acids in lipids and oils to cause salt formation (soap). Membrane disruption leads to cell wall destabilization (in case of gram negative bacteria) and loss of membrane structure and function, including disruption of the proton motive force and leakage of cytoplasm materials. Alkalis also cause breakage of peptide bonds and the breakdown of proteins, which is presumed to be the major mechanism of action against prions.
High concentration (0.5 to 2.0 N) of sodium and potassium hydroxide are used for cleaning and disinfecting manufacturing surfaces to inactivate bacteria, viruses and prion contamination. Prolonged exposure is often required to achieve ideal effect of sterilization on the surfaces treated with these alkali solutions. Alkali solutions are also effective in emulsifying and saponification of fats and removal of proteins as these are broken down to peptides and amino acids. Sodium bicarbonate is also used as a deodorizer. Higher alkalinity inhibits microorganisms, with the exception of certain thermophiles; in general, pH values greater than 9 are restrictive for growth of most vegetative organisms, including bacteria and fungi. Lower concentrations are generally inhibitory, while higher concentrations are bactericidal and fungicidal. Typical virucidal concentrations are 1-2% of sodium hydroxide and at least 4% sodium carbonate; concentrations of 1-2N of sodium hydroxide are recommended for the inactivation of prions. The main advantage of alkali use is their wide availability, low cost and a wide range of bacteriostatic and bactericidal activities obtained. More particularly, the combination of effect on fats and proteins, they offer an ideal solution to removing allergens. The disadvantages in their use include their highly corrosive nature to many surfaces, danger to human contact and the possibility of violent reaction if mixed with certain organic or inorganic substances.
The present invention provides a device for scrubbing of air through a high pH chemical solution of an alkali that can be used in confined spaces, in central air conditioning systems of patient care, home care to reduce allergies, by defense personnel as part of biological agent protection strategy, in drug manufacturing facilities and in public places to reduce spread of disease such as flu epidemic, such as the swine flu.